It has long been the practice in the tire curing art to counter the extreme forces created by the introduction of high pressure fluids interiorly of a tire positioned within mold sections by use of heavy mechanical components in the design of tire curing presses. The most successful and commonly employed mechanical designs have included base and cross beam elements of heavy steel with reinforcing design to minimize the deflection produced by the forces and moments developed during press loading. The closing of the mold sections effected by movement of the cross beam and the application of sufficient squeeze or closing force to maintain the mold sections closed during the curing operation have been produced by toggle mechanisms consisting of bull gears trunnion mounting side links which are attached to the cross beam by second trunnions. Further, large side plates have been employed to control the movement of the second trunnions in selected cam slots therein to dictate the path and orientation of the cross beam involved in travel of the press cross beam from the closed to the open position.
Besides the size and complexity of conventional mechanical drive mechanisms for tire curing presses, the interrelation of the conventional components has resulted in presses of very large size and weight, particularly as the size and pressures involved in curing presses for larger tires are accommodated. Such size, weight and complexity have also translated into very high manufacturing, transportation and installation costs. It has also been recognized that the size, complexity and interrelation of conventional press elements have been such that the introduction or addition of insulating materials to reduce operating costs is not readily accomplished, whereby substantial energy inefficiencies have long been tolerated in regard to tire curing presses.
While it has been recognized for some time that a hydraulically actuated press could provide substantial advantages as contrasted with conventional mechanical operation, in the context of a simple vertically opening press, a number of serious deterrents have been encountered in efforts to develop successful hydraulically actuated tire curing presses. Due to the complexities involved some hydraulic presses have not employed positive locking devices which preclude opening during the press curing cycle to counteract the pressures within a tire being cured. In other instances, interlocking elements associated with the upper and lower mold sections or elements associated therewith have been employed to effect a requisite locking engagement precluding press opening in the event of hydraulic pressure failure. Whether or not provided with high pressure preloaded interlocking engagement, bayonet type lock mechanisms have been proven to be relatively complex and expensive and to require additional press components in the nature of mold height adjustment apparatus for the differing mold heights commonly processed in tire curing presses of any size.
In general, hydraulically actuated press designs to the present time which have solved the above problems have resulted in a press of size, weight and complexity comparable to conventional mechanical presses with the recognized disadvantage of a hydraulically operated device in a rubber processing facility.